The semiconductor chip industry has developed1 "chip scale" packages for protecting an integrated circuit on a semiconductor die and for providing wire connections from the integrated circuit to other circuits outside the chip. An example of a conventional chip package is a flex/tape-BGA package, which includes a semiconductor die directly attached to an interposer. The flex/tape-BGA package allows for a constant package body and a constant solder ball pattern independent of the size of the die to some extent. However, the flex/tape-BGA package requires a rigid connection between the die and the interposer, thereby resulting in a problem of decreased solder joint reliability. Examples of the flex/tape-BGA package include Texas Instruments Microstar.RTM., Fujitsu FBGA and Amkor FlexBGA.RTM. packages.
Another type of a conventional chip package is a microBGA.RTM. package, an example of which is developed by Tessera Inc. The microBGA.RTM. package generally has an improved solder joint reliability compared to the flex/tape-BGA package. The microBGA.RTM. package includes tab-like bonds for providing electrical connection between the semiconductor die and solder balls outside the interposer. However, the design of the interposer in the microBGA.RTM. package is governed by the die size and the bond pad position, and is very sensitive to changes in the die size. In a conventional microBGA.RTM. package, a different interposer design with a different tab bond and solder ball pattern is usually required for any change in die size.
Therefore, there is a need for an integrated circuit chip package that simultaneously provides both a good solder joint reliability and a single interposer design with a constant tab bond and solder ball pattern that can accommodate a variety of die sizes.